Multithreading on Linux

[Drew Lane]

I understand that Solaris uses preemptive tasking for multithreading, and that Windows uses timeslicing, but what does Linux use (with respect to Java, of course)?
Thanks!
Drew
[ November 13, 2002: Message edited by: Drew Lane ]

[Marcos R Oliveira]

Hi, Drew!
I am not sure what type of tasking Linux uses, but below is a code that can help you to find out.
If you run the application and the messages "Foo" and "Bar" alternate then Linux uses timeslicing. If "Bar" is never printed then Linux uses preemptive multitasking.

  
public class Thready1 {
    public static void main( String args [] ) {
        new MinhaThread("Foo").start(  );
        new MinhaThread("Bar").start(  );
    }
}
class MinhaThread extends Thread {
    String mensagem;
    MinhaThread ( String mensagem ) {
        this.mensagem = mensagem;
    }
    public void run(  ) {
        while ( true )
          imprime();
    }
    public synchronized void imprime() {
      notify();
      System.out.println( mensagem );
      try {
        wait(1000);
      } catch (InterruptedException e) { }
    }
}

Hope this can help you,
Marcos.

[Ron Newman]

Why would preemptive multitasking prevent the "Bar" thread from running? When "Foo" notifies and waits, that should be enough to wake "Bar" up.

[Marcos R Oliveira]

Oh! I�m sorry!
In the code above I put a wait() call and the method imprime() to make a test. The code below is what I wanted to show here.

public class Thready1 {
    public static void main( String args [] ) {
        new MinhaThread("Foo").start(  );
        new MinhaThread("Bar").start(  );
    }
}
class MinhaThread extends Thread {
    String mensagem;
    MinhaThread ( String mensagem ) {
        this.mensagem = mensagem;
    }
    public void run(  ) {
        while ( true )
          System.out.println( mensagem );
    }
}

With this example, in a preemptive multitasking, "Bar" will never have the chance to be printed, while in a timeslincing "Foo" and "Bar" can be seen.
Thanks, Ron,
Marcos.

[Ron Newman]

On MacOS X 10.2.2, which is based on BSD Unix, you see both "Foo" and "Bar'", but they do not alternate one for one. Instead, I get long stretches of Foo, followed by long stretches of Bar, then back to Foo, etc.

[Jose Botella]

It happens the same in Mandrake 9.0

[Barry Gaunt]

On Suse 8.1 it gives a couple of hundred Foos then sticks a few seconds, and then goes into a Foo-Bar flip-flop.
-Barry
[ November 15, 2002: Message edited by: Barry Gaunt ]